Normally, shivering is an involuntary response to cold that kicks in once core body temperature drops below 36.6 degree Celsius or when skin temperature falls below 28 degree Celsius.
This is usually beneficial, as the muscle contractions generate heat, but in cold water it only serves to increase the rate at which the human body cools. That's because the increased blood flow transfers more heat from the core to the body's extremities, fingers and toes.
It is the availability of fresh water, which determine the core temperature is maintained for optimal functions of the various inner organs of the body.
It is a misconception that hot drink will warm up the inner body, or ice-cold/chilled drink will 'cool' the body.